Study On The Deposition Law Of Cyhalofop-methyl In Leptochloa Chinensis (L.) Nees

Leptochloachinensis(L.)Nees.is increasingly harmful to rice and has a tendency to spread rapidly.The environmental factors that have the greatest impact on the control effect are temperature,air relative humidity(RH)and drought stress,the application factors include droplet size and liquid application rate.In this study,in order to effectively prevent Leptochloa chinensis(L.)Nees and provide theoretical guidance for controlling Leptochloa chinensis(L.)Nees.by cyhalofop-butyl,we studied the effects of environmental factors and application factors on the biological activity of Leptochloachinensis(L.)Nees.biotype from Zhejiang province to cyhalofop-butyl and the effect of application factors on the deposition of cyhalofop-butyl in the leaves of Leptochloachinensis(L.)Nees.The results of the study are as follows:1 Sensitivity of Leptochloachinensis(L.)Nees.in Different Areas of Zhejiang Province to cyhalofop-buty.The results showed that the efficacy of 5 Leptochloachinensis(L.)Nees.biotypes from Zhejiang province reached more than 90%at a dose of 105 g a.i./hm~2 by whole-plant assay.It indicate that the 5 biotypes were sensitive to Cyhalofop-methyl.In this study,TZ029 was used as the material for the following experiments,which is a typical and biotype in Zhejiang Province.2 Effects of different factors on biological activity of cyhalofop-butyl(1)Envirnmental factorsThe three environmental factors had an impact on the biological activity of cyhalofop-butyl using the whole-plant assay with the model No.ST110-01 nozzle of TZ029 biotype.The results as follows:When the dosage was 9.94 g a.i./hm~2,and Leptochloa chinensis(L.)Nees.was cultivated in the temperature range of 5-35℃,the biological activity of cyhalofop-butyl was increased with the increase of temperature,but the difference was not significant.When the temperature control(day/night)at 15/5℃,25/15℃,and 35/25℃,the fresh weight control effect of Leptochloa chinensis(L.)Nees.was 43.10%,51.33%,and 61.80%,respectively.When the dosage was 9.94 g a.i./hm~2 and the relative humidity(RH)is in the range of20%-95%.the biological activity of cyhalofop-butyl was increased with the increase of RH.When the RH was 20%,45%,70%,and 95%,the control effect of cyhalofop-butyl chlorate on the Leptochloa chinensis(L.)Nees.was 46.77%,69.57%,70.89%,and 77.13%,respectively.There was no significant difference among 45%,70%and 95%,but they were significantly different from20%.Drought Stress reduces bioactivity of cyhalofop-butyl.When the dosage was 9.94 g a.i./hm~2and 57.53g a.i./hm~2,the control effct of drought stress was significantly lower than that of conventional treatment with a decrease of 7-10%,and the difference was significant.(2)Application factorsThe control effect of cyhalofop-butyl to Leptochloachinensis(L.)Nees.was reduced with the increase of VMD When the liquid application rate was 350 L/hm~2,the amount of cyhalofop-butyl was the same and five spray heads were used for spray treatment(drop diameter VMD ranged from149.5 to 233.7μm).When the dosage was 9.94 g a.i./hm~2,There were significant difference between the treatment with VMD of 149.5,157.3μm and the treatment with VMD of233.7μm.When the dosage was increased to 57.53 g a.i./hm2,there were significant difference between the VMD of 233.7μm and the other four treatment,but there was no significant difference in the four treatments.When the dosage was 9.94 g a.i./hm~2 and the liquid application rate was in the range of175-700 L/hm~2 with the ST110-01 model nozzle,the control effect of cyhalofop-butyl to Leptochloachinensis(L.)Nees.was reduced with the increase of liquid application rate.When the liquid application rate was 175 L/hm~2,the maximum control effect was 86.61%,which was about 2times the control effect at 700 L/hm~2.There was a significant difference between the two.3 The effect of application factors on the deposition of cyhalofop-butyl in the leaves of Leptochloachinensis(L.)Nees.liquid application rate.When theliquid application rate was in the range of 175-700 L/hm~2,the deposition of cyhalofop-butyl in the leaves of Leptochloachinensis(L.)Nees.were decreased with the increase of theliquid application rate.When theliquid application rate dropped to 87.5 L/hm~2,the deposit rate was 5.07μg a.i./hm~2,which is significantly smaller than 5.94μg a.i./hm~2 at 175 L/hm~2.When the VMD was in the range of 149.5-233.7μm,the deposit rate was decreased with the increase of VMD.The deposit rate at the VMD of 149.5μm was 2.17 times that at 233.7μm,and the difference was significant.The VMDs were 149.5,157.3,193.2,215.4 and 233.7μm,corresponding to theliquid application rate of 175.00 L/hm2,309.75,405.79,514.56 and 631.73L/hm~2 respectively.The deposit rate was decreased with the increase of VMD andliquid application rate.Wjen the VMD was 149.5μm andliquid application rate was 175 L/hm~2,the deposit rate was the largest,which was significantly different from the other four groups.4 Maximum stable retention of of cyhalofop-butyl in the leaves of Leptochloachinensis(L.)Nees.The maximum stable retention on the leaves of Leptochloachinensis(L.)Nees.was 7.71μg/cm~2 sprayed with 300 mg a.i./L of the cyhalofop-butyl with the ST110-01 model nozzle.When theliquid application rate was in the range of 150-900 L/hm~2,the deposit rate was increased with the increase of theliquid application rate.When theliquid application rate was in the range of900-1050 L/hm~2,the deposit rate did not increase any more.